The gut microbiota is currently considered to be an essential factor for the gut health and well-being of the host. Colonization of the gut by beneficial bacteria plays a key role, preventing the growth of pathogenic bacteria.

There are numerous theories about how beneficial microbes prevent pathogen colonization, such as the one that suggests that non-pathogenic bacteria bind to intestinal cells, occupying the site of pathogens and reducing their chance of binding and colonization. It has also been proposed that these microorganisms synthesize substances such as volatile fatty acids, organic acids and natural antimicrobials that impede microbial growth or make the environment unsuitable for non-beneficial bacteria. The gut microbiota has also showed to increase the expression of ocludine and claudine (proteins that form the narrow bonds between enterocytes). It is also worth mentioning that it collaborates in the development of the immune system

The traditional way of managing pathogens through the use of large amounts of chemicals (zinc, copper, antibiotics) has been limited. Since 2006, when the ban on the use of growth-promoting antibiotics in the European Union came into force, the search for different strategies for controlling and modulating the gut microbiota has been promoted.

The composition of the gut microbiota is known to affect many host functions, including nutrient utilization, intestinal epithelium integrity, and the development and activity of the intestinal immune system. Therefore, one of the possibilities to reduce pathogen colonization and antibiotic use in animal production is to keep the gut microbiota balanced.

Characteristics and challenges of the microbiota in pigs

• Characteristics of the microbiota in pigs

The microbiota of a mammal’s intestine is populated by approximately 100 trillion bacteria that provide benefits to the host through the production of short-chain fatty acids and vitamins, inhibition and prevention of pathogen colonization, and by contributing to the development and maintenance of the immune system.

In the case of pigs, at birth, they receive much of the gut microbiota from their mother. The transfer occurs through different pathways: the earliest route is the systemic transfer from the maternal intestine to the breeding pups that are being gestated. Subsequently, the bristles end up contributing to the microbiota of piglets through contact in the birth canal, colostrum, breast milk, and by bacteria present in feces and skin.

The digestive microbiota varies throughout the life of the animal to adult life, when it becomes stable. This change is affected by multiple factors, such as the environment or diet, among others.

The distribution of the gastrointestinal microbiota along the tract depends on the pH, oxygen pressure and the rate of content transit, mainly. For this reason, the distribution is not uniform throughout the gastrointestinal tract, but varies the concentration and genera of bacteria we find.

In pigs, both the stomach and the most cranial part of the duodenum are characterized by being the most acidic pH portions, having a rapid transit, which limits adhesion and bacterial colonization. These factors make the bacterial concentration lower than in the most distal area and the genera of bacteria present are the most resistant to this hostile pH: Lactobacillus, Streptococcus and Enterococcus, predominantly.

The concentration of bacteria increases from 10⁵ bacteria/g in the small intestine to 10¹⁰-10¹² bacteria/g in the large intestine. This is because, in the distal portion of the intestine, conditions are more appropriate and stable for bacterial growth due to more neutral pH, slower transit and the anaerobic environment. In the large intestine the predominant bacterial families are Clostridiacea, Enterobacteriaceae, Bacteroidaceae and Veillonellaceae.

• Challenges for the microbiota in pigs

Several factors can influence the balance of the gut microbiota, the most important are the use of antibiotics, stress and management practices (hygiene, nutrition, weaning). On the other hand, balance can be maintained with the use of pronutrients.

In the pig industry, piglets are weaned early to reach productive targets, when the microbiota is not yet stable and the immune system is still immature. This practice causes great stress in piglets, which increases their susceptibility to bacteria that cause diarrhea.

Post weaning diarrhea causes major economic losses. This is characterized by an imbalance of the microbiota with an increase in pathogenic bacteria. The main factor that induces this dysbiosis is the low ingestion of feed and water after weaning, since the piglets are stressed and go from a liquid diet to a solid one, to which they must adapt. This anorexia leads to changes in the gut and an increase in pH by reducing lactic acid-producing microbiota bacteria, increasing the likelihood of pathogenic bacteria replication.

Another common cause of alteration of the gut microbiota is the sustained use of antibiotics, especially in young animals, because it affects the establishment of the microbiota and can have a long-term effect. This is one of the reasons to seek for a reduction of the use of antibiotics, which can be replaced by naturally occurring additives.

Characteristics and challenges of the microbiota in birds

• Characteristics of the microbiota in birds

The microbiota of the gastrointestinal tract of birds is essential for the maintenance of intestinal homeostasis, host metabolism and for its importance on the physiology and health of animals, which allows to achieve the expected performance.

This microbiota begins to populate the intestines of birds immediately after hatching, when they contact the microbes present in the incubator. After arriving at the farm, with the consumption of water and feed, the birds experience a rapid acquisition of microorganisms. Throughout the life of animals, various changes occur in their microbiota.

The gastrointestinal tract of birds differs from that of mammals by being shorter and having a faster transit. These conditions make the gut microbiota of birds very different from that of other species in terms of concentration and bacterial genera.

The distribution and genera of bacteria present vary throughout the gastrointestinal tract, due to differences in pH, anaerobiotic conditions, osmolarity and the presence of substrates, similar to what happens in pigs.

In the proximal portion of the gastrointestinal tract, the bacterial concentration is lower, in the ileum there are 10^8-9 CFU/g of content and then it raises, reaching in the colon and ceca a concentration of 10^10-11 CFU/g of content. The ceca in birds differ from the rest of the intestine, as they are able to store content for a long time, which makes them have diverse and stable microbiota. This organ is of fundamental importance in the digestion of fiber and synthesis of some B vitamins.

• Challenges for the microbiota in birds

Broiling chickens and laying hens share the predominant phylum in their microbiota: Firmicutes, Bacteroidetes and Proteobacteria, however, the proportion of each varies.

The bacterial genera of these phylum present in the ileal mucosa are predominantly Lactobacillus, followed by Clostridium, Streptococcus and Enterococcus, while in colon and ceca the genera Eubacterium, Bifidobacterium and Clostridium predominate. Within the genera that normally inhabit the digestive tract of birds, some are potentially pathogenic, such as Clostridium perfringens, the etiological agent of necrotic enteritis. The balance of the microbiota is key to prevent this disease of high impact in poultry production.

During its lifetime, a bird will face many challenges to maintain the stability of the microbiota, among the most important and that are present in any commercial production system we find: vaccination, use of antibiotics, changes of feed, inadequate temperature or ventilation and infections by viruses, bacteria or parasites.

It is very important to maintain favorable intestinal conditions with the correct balance of microbial species throughout the life of the bird, to avoid that the challenges cause a decrease in productive performance.

Strategies for the control and improvement of the microbiota

Nowadays, in animal production, it the stability of the microbiota must be considered, particularly, and gut health in generally, as key objectives to have a sustainable production system that allows animals to achieve their maximum performance.

The use of antibiotics to reduce pathogens is an increasingly limited option and instead of them, new alternatives emerged that aim to achieve the following objectives:

• The establishment of favorable bacteria as soon as possible in the life of the animal.
• The creation of a suitable microenvironment in the gut to support the proliferation of favorable bacteria.
• The reduction, as much as possible, of the indigestible substrates that are potential food for unwanted bacteria.

To meet these objectives, there are different additives:

• Botanical microbiota modulators

They are naturally occurring substances with antimicrobial capacity. This is the case of the cimenol ring, a substance that is present in different aromatic plants (thyme, rosemary, sage, etc.) and acts as an intestinal biocide, controlling pathogenic bacteria (Clostridium, Salmonella, E. coli) and favoring the development of beneficial bacteria.

The effect of the cimenol ring can be boosted by combining it with citric acid (Alquermold Natural), because they act synergistically: citric acid generates pores in the bacterial membrane, facilitating the entry of the cimenol ring into the bacteria, causing the destabilization of the plasma membrane and death by osmotic shock. The combined action of these two active compounds has been patented by Biovet S.A, which has studied this mechanism of action through its R&D department.

In addition, the cimenol ring also inhibits the synthesis of ergosterol, an important steroid in the membranes of fungi, exerting its fungicide effect.

Alquermold Natural has a dual effect since, in addition to being an intestinal biocide, it is a preservative of raw materials and compound feed. Microbiological control of the feed also influences the balance of the microbiota due to the reduction of the challenges that generate a high load of microorganisms. In addition, it is a safe product that does not generate bacterial resistance, lacks withdrawal period, and leaves no residue.

The product is marketed by BIOVET S.A under the trade name Alquermold Natural. Available in Premix and liquid presentations.

• Intestinal conditioner pronutrients

They are complex molecules of plant origin that improve intestinal physiology, the mechanism of action has been studied by Biovet S.A based on the metagenetic action of the stimulation of specific DNA genes with specific functions in enterocytes. They act as an external stimulus by increasing the synthesis of functional protein by enterocytes, which is reflected in a greater regeneration of intestinal mucosa cells, increasing the absorption of nutrients. They also improve tight junctions between enterocytes, which are key for intestinal integrity.

A conditioned mucosa will allow and facilitate the establishment of beneficial microbiota, which, by competitive exclusion, does not allow the development of pathogenic bacteria.

Pronutrients exert their beneficial effect by improving both nutrient absorption and microbiota; a better use of nutrients present in the diet prevents the development of pathogenic bacteria, favoring the growth of beneficial ones. This results in better production rates, conversion rate, weight, meat quality, egg quality, etc.

Pronutrients meet market and consumer requirements, do not generate bacterial resistances, lack withdrawal periods, and leave no residues in meat, milk and eggs. They are suitable for organic production.

It has been observed that the effect of these pronutrients is greater in young animals, as they also help in the development of the digestive system and adaptation to new diets.

Biovet S.A has patented this technology, marketed under the name Alquernat Nebsui. It is available in premix and liquid presentations and suitable for birds and pigs

• Probiotics

They are microbial strains beneficial for health. Early seeding of the gut animals with these beneficial bacteria helps to prevent the overgrowth of pathogenic bacteria. At the same time, it facilitates the establishment of a well-balanced, diverse and properly-working microbiota.

Biovet has developed Alquerfeed Probiotic, a combination of microorganisms that colonize intestinal spaces, acidify the environment, and synthesize enzymes and bacteriocins. This action leads to a repopulation of the intestinal tract, inhibiting the presence of pathogenic bacteria. This way they improvement feed digestibility.

• Enzymes

Additives formulated with exogenous enzymes, such as Alquerzim, are also related to the balance of the microbiota.

Enzymes are proteins that act on specific substrates, catalyze biochemical reactions by accelerating them. Their activity depends on temperature and pH.

Exogenous enzymes aim to improve digestibility by promoting proper nutrient utilization, reducing feeding costs and improving production rates.

The best use of nutrients will have a positive impact on the microbiota, for example, poor absorption of proteins predisposes to the development of Clostridium perfringens, which can be corrected with the addition of exogenous proteases.

The enzymatic composition of this type of additive should be adapted to each diet, age and species. Biovet has developed the Alquerzim line with specific enzyme combinations that adapt to the needs of each holding.

Conclusions

In animal production, the stability of the microbiota should be considered as a key objective to achieve gut health. The balance of the microbiota is of paramount importance to minimize health problems in production animals and to achieve maximum productive yields by accompanying the pace of genetic advances.

As part of the same strategy to meet our objective, the establishment of the right microbiota in the early stages of life helps animals to face the normal challenges of the production system, ensure the quality of the diet and that there are no imbalances of the microbiota caused by the indiscriminate use of antibiotics that can be replaced with natural additives, such as pronutrients, the cimenol ring, probiotics and enzymes.